Fifty Shades Ltd., the original copyright holder of E.L. James' Fifty Shades of Grey, and Universal Pictures, which controls the movie rights, are suing the makers of a porn flick dubbed Fifty Shades of Grey: a XXX Adaptation, alleging they're violating the copyright and trademark on the best-selling trilogy and creating confusion in the marketplace.

Per the lawsuit filed in Los Angeles and obtained by E! News, the plaintiffs claim Smash Pictures and adult video director James Lane, who's credited onscreen as Jim Powers, have engaged in a "willful attempt to capitalize on the reputation of the book."

According to court docs, the studio and Fifty Shades Ltd. argue that Smash honcho Stuart Wall declared his intentions to essentially make a knockoff of the popular BDSM-themed novel about a college graduate named Anastasia Steele and her kinky affair with Christian Grey, a wealthy businessman.

As evidence, the suit points to an interview Wall gave LA Weekly last summer in which the executive was quoted as saying, "Since they are going to make a mainstream [movie] of the books, too, dabbling in the adult world we're choosing to go with a XXX adaption which will stay very true to the book and its S&M-themed romance."

That didn't go over so well with Universal and company. "By lifting exact dialogue, characters, events, story, and style from the Fifty Shades trilogy, Smash Pictures ensured that the first XXX adaptation was, in fact, as close as possible to the original works," states the suit.

Universal and Fifty Shades Ltd. must have procured a copy somehow, because their complaint then lists in detail the supposed violations.

"Beginning with the first XXX Adaptation's opening scene and continuing throughout the next 2½ hours of the film, Smash Pictures copies without reservation from the unique expressive elements of the Fifty Shades trilogy, progressing through the events of Fifty Shades of Grey and into the second book, Fifty Shades Darker," reads the suit. "The first XXX adaptation is not a parody, and it does not comment on, criticize, or ridicule the originals. It is a rip-off, plain and simple."Another defendant named in the action is distributor Luv Moves, which has been accused of including sex toys with the DVD in a kit called Fifty Shades of Pleasure: Play Kit & Movie.

Universal, which is in the process of developing its own big-screen version of the steamy best-seller, and Fifty Shades are asking a court to issue an injunction and award monetary damages.

Reps for Universal and Smash Pictures declined to comment on the litigation.